NA-TT Diff advice

My car is a '94 SZ with a TT conversion.

It has no ABS, no TC, no LSD (just an open diff I believe).

As it has the W58 5 speed box it is fairly quick (acceleration) given the ratios.

It is only a 1st decat short of being full BPU (grade 7 NGK iridium plugs, RSR exhaust, 2nd decat, HKS SLD, HKS FCD, Greddy 2 row FMIC, Envy 1.2 bar RR) at the moment too, so obviously that decat will push it up a considerable amount!

What I'm wondering is, when it comes to changing the diff to an LSD at some point, what is required to do so and which would be best for acceleration? TT Auto? Is that doable?

Any info greatly appreciated, I'm quite in the dark with regards to all this diff talk!

Well, I'm not really sure about a tt auto diff in combination with an W58, i used to have the W58 with an standard delivered trd diff (not the torsen one)

Coverted into a TT auto diff(A02B-Torsen diff) in combination with a getrag 6 speed (v160),

TT auto diff versus TT Manual diff

Manual TT diff longer gears higher top speed

TT auto diff shorter gears lower top speed

TT auto diff my expierience is telling me that it takes less time to achieve top speed, it will be lower then the top speed which can be achieved by having a TT manual diff.

Fuel consumption is a lot higher having a TT auto diff but worth every euro of fuel spend

This is a copy paste from .COM.NZ

Torsen LSD vs TRD LSD

The Torsen diff is a standard fitment to all 6 speed mkiv's, alot of the Auto TT's and you'll even occasionally find it on a NA. You can tell if your Supra has a Torsen diff by reading the Trans/Axle code on the Engine Tag which is situated under your bonnet. The last letter of the 4 character code (eg. B03B) denotes the diff type which is "A" for a std diff and "B" for a Torsen diff. The crown wheel on the B series is 220mm whilst on the A series it's 200mm.

The Torsen (TORque SENsing) LSD (Limited Slip Diff) works quite differently to the TRD LSD. The Torsen is a Torque Multipling type of diff with a multiplication ratio of around 5:1. What this means is that whatever torque can be sent to the wheel with the least traction, it can send up to 5 times that torque to the wheel with the most traction. Its biggest advantage is that it can do this extremely quickly and doesn't ever lockup the ratio, but is continuously "sensing" and adjusting the torque between the two wheels. Its only real disadvantage is that when one wheel has no torque available (say it spinning in mud), then 5 times nothing is still no torque to the other wheel, so you can get stuck just like a std diff. Once the car is moving however this cannot happen. The TRD LSD is a standard type LSD in that it uses clutch packs to transfer torque from one wheel to the other. Transferring torque via clutch packs will be a slower process then the Torsen transfer method and it will absorb more energy from the engine when doing so. However we are probably only talking a few hundreds of a second difference here and maybe a few hp. The main disadvantage of the TRD diff is that it can "lockup" the ratio between the two wheels at 1:1. This means both wheels will then turn at the same speed and if this happens on a corner, it would be exciting at the very least. This "lockup" is also its only advantage over the Torsen diff as even when one wheel is in the mud, the other wheel can provide traction to pull you out.

My personal preference is for the Torsen diff as it usually comes free with the car, reacts quicker and aborbs less power and will never accidentally lockup. However, if you want to go rally driving in your mkiv Supra (don't laugh, there's guys in the USA that do just that) then the TRD would be the better bet.

Mario has answered it in part, but got some things a little mixed.

With the w58 your really should try and retain the diff ratio of the NA (4.083), if you move to a TT auto diff the ratio gets longer (3.769) and will mean a higher top speed in each gear at the cost of slower acceleration.

If possible I'd try to get an NA LSD diff. The diff itself and casing is the same as the TT small casing options, however the CP are different. It's the CP that is generally the weak spot in the NA diff, (but *should* be okay for TT power), I'm trying to find option for a stronger CP for my own car.

If you've not found it already you can play around with the ratio's and diff options in this calculator: http://www.mkivsupra.net/vbb/showthread.php?225050

Good reading, insightful! Thank you guys!

Sounds like I should try to find an LSD as equipped standard on the SZ-R.

Mario has answered it in part, but got some things a little mixed.

 

With the w58 your really should try and retain the diff ratio of the NA (4.083), if you move to a TT auto diff the ratio gets longer (3.769) and will mean a higher top speed in each gear at the cost of slower acceleration.

 

If possible I'd try to get an NA LSD diff. The diff itself and casing is the same as the TT small casing options, however the CP are different. It's the CP that is generally the weak spot in the NA diff, (but *should* be okay for TT power), I'm trying to find option for a stronger CP for my own car.

 

If you've not found it already you can play around with the ratio's and diff options in this calculator: http://www.mkivsupra.net/vbb/showthread.php?225050

TT BPU power or just TT power?